1926 Wild Heerbrugg NKII

Figure 1: The 1926 Wild Heerbrugg NKII.

During a house clearing here in the Netherlands in 2013 the company commissioned to do the job found a little metal container. Initially they could not open it and it almost ended up in the skip. Just before that actually happened they gave it another, this time successful, attempt to find out it contained this little level made by the Swiss company Wild Heerbrugg.

The metal container (see figure 4) was the original one belonging to this very rare instrument, one of the very first Wild levels. Being a level (Nivellier in German) and having a graduated horizontal circle (Kreis in German) the model was dubbed "NKII". This method of naming their models was the way Wild would use for their levels in later years, although the Roman numerals were soon replaced by Arab numerals, like in the 1951 Wild N2.

When Heinrich Wild started his own company the first instrument he produced in 1923 was the NII (so yet without the Kreis). The NKII model would follow the year after. This particular one shown here with serial number 960 was part of a series of 100 instruments bearing serial numbers 912 - 1011, which were produced from 1925 onwards.1 Most likely it was made in 1926, the year Wild Heerbrugg produced their first theodolite, the archetype Wild T2.

Figure 2: The 1926 Wild Heerbrugg NKII from the other side.

ProvenanceThe NKII once belonged to one C.M. Bus, but no more particulars are known of him, apart from the fact that he died some 20 years ago and that the house was cleared because his wife had recently died.

DevelopmentWhen comparing the NKII with the 1924 Carl Zeiss Nivellier II it is obvious that they originate from the same brilliant mind (see figure 3). Both were designed by Heinrich Wild, the latter during his years as manager at Carl Zeiss Jena, the former after having founded his own company.

Both instruments were designed along the same lines. The same type and positions of both the plate and circular level can be found on both of them.

The main differences were the addition of the horizontal circle and the roughly one third in reduction of its size. The size reduction meant that the instrument could no longer be reversed, making it a tilting level like - but more accurate than - the Wild NK10 in the collection. This functionality would however soon come back as can be seen it its successor, the Wild N2. Over the years the NK2 was fully redesigned twice, a development that can be seen in the 1951 version and the 1970 version of this levelling instrument.

Accuracy

The Wild NKII was not coincidently roughly as accurate as the 1924 Carl Zeiss Nivellier II. With 175 millimetres the telescope may have been much shorter than the 285 millimetres one of the Nivellier II, its aperture of 40 millimetres and magnification of 24 times are roughly the same (respectively 35 millimetres and 28 times).2 It gives an inverted view with two stadia hairs with a multiplication constant of 100 along the vertical cross-hair (see figure 12).

The coincidence vial is almost as large as the telescope and has an accuracy of 20" per 2 millimetres run, just like the Nivellier II.

The horizontal glass circle measures 50 millimetres in diameter, is divided in whole degrees (they were also produced with centesimal divided circles) and can be read using the scale microscope at 30 times magnification directly to 10 arc minutes, while estimation to single arc minutes is possible (see figure 13). The circle is fully visible around the primary axis, but being made of glass the graduations are fully protected (see figure 7 and figure 9). For additional light a tiny reflector - one side white, the other a mirror - was mounted below the microscope (see figure 8).

The instrument

The Wild Heerbugg NKII came complete with its original container. Apart from some delamination round the edges of the achromatic objective lens (see figure 12) the instrument is in very good order and still fully functional. Interesting is the colour: it is a kind of greenish grey to distinguish it from the Carl Zeiss instruments (see figure 3). This greenish grey would soon become the typical green as known from later Wild Heerbugg instruments like the 1929 archetype Wild T2.

Notes

[1]: With many thanks to J. Dedual of the Virtual Archive of Wild-Heerbrugg for checking the serial for me.[2]: Wild Heerbrugg, Wild Geodätische Instrumente, Druckschrift Geo. 15., (Heerbrugg, 1930), pp.5-8.